U.S. patent number 6,138,636 [Application Number 09/317,622] was granted by the patent office on 2000-10-31 for apparatus for controlling multi-cylinder internal combustion engine with partial cylinder switching-off mechanism.
This patent grant is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Eitetsu Akiyama, Morio Fukuda, Ryuji Kohno, Toshiyuki Suzuki.
United States Patent |
6,138,636 |
Kohno , et al. |
October 31, 2000 |
Apparatus for controlling multi-cylinder internal combustion engine
with partial cylinder switching-off mechanism
Abstract
In an apparatus for controlling a multi-cylinder internal
combustion engine with partial cylinder switch-off mechanism which
is switchable between an all-cylinder operation mode in which all
cylinders are operated and a partial-cylinder operation mode in
which operation of partial cylinders is suspended, the operation of
intake valves and exhaust valves is suspended or resumed in a
predetermined order with respect to all of the suspended cylinders
irrespective of a rotational frequency of the engine. There are
provided a solenoid valve on an intake side and a solenoid valve on
an exhaust side for switching input hydraulic pressures for
hydraulically operated switching devices respectively on the intake
side and on the exhaust side between the driving state and the
drive-free state. At the time of switching the operation, one of
the solenoid valves on the intake side and the exhaust side is
driven in advance. The subsequent number of rotations of a
crankshaft is counted. When the number of this counting has reached
a predetermined value, the solenoid valve on the other side is
driven.
Inventors: |
Kohno; Ryuji (Tochigi-ken,
JP), Suzuki; Toshiyuki (Tochigi-ken, JP),
Akiyama; Eitetsu (Tochigi-ken, JP), Fukuda; Morio
(Tochigi-ken, JP) |
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha (Tokyo, JP)
|
Family
ID: |
27318806 |
Appl.
No.: |
09/317,622 |
Filed: |
May 25, 1999 |
Foreign Application Priority Data
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May 26, 1998 [JP] |
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10-144344 |
May 26, 1998 [JP] |
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10-144345 |
May 26, 1998 [JP] |
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10-144346 |
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Current U.S.
Class: |
123/198F |
Current CPC
Class: |
F02B
75/22 (20130101); F02D 13/06 (20130101); F01L
1/267 (20130101); F01L 13/0005 (20130101); Y02T
10/12 (20130101); F01L 2201/00 (20130101); F02D
2041/0012 (20130101); Y02T 10/18 (20130101) |
Current International
Class: |
F02D
13/06 (20060101); F02B 75/22 (20060101); F01L
13/00 (20060101); F02B 75/00 (20060101); F01L
1/26 (20060101); F02D 013/06 () |
Field of
Search: |
;123/198F,90.15,90.16 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 573 662 A1 |
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Dec 1993 |
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EP |
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2 101 683 |
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Jan 1983 |
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GB |
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Primary Examiner: Wolfe; Willis R.
Assistant Examiner: Ali; Hyder
Attorney, Agent or Firm: Armstrong, Westerman, Hattori,
McLeland & Naughton
Claims
What is claimed is:
1. An apparatus for controlling a multi-cylinder internal
combustion engine with partial cylinder switch-off mechanism, said
engine being switchable between an all-cylinder operation in which
all cylinders are operated and a partial-cylinder operation in
which operation of partial cylinders is suspended, said apparatus
comprising:
hydraulically operated valve switching means on an intake side and
on an exhaust side, respectively, for switching intake valves and
exhaust valves of the partial cylinders between a driving state and
a drive-free state, wherein said intake valves and said exhaust
valves of the partial cylinders are switched, during the
partial-cylinder operation, into the drive-free state;
a control valve on the intake side for switching a hydraulic
pressure inputted to said hydraulically operated valve switching
means on the intake side between a hydraulic pressure to bring said
intake valves into the driving state and a hydraulic pressure to
bring said intake valves to the drive-free state;
a control valve on the exhaust side for switching a hydraulic
pressure inputted to said hydraulically operated valve switching
means on the exhaust side between a hydraulic pressure to bring
said exhaust valves into the driving state and a hydraulic pressure
to bring said exhaust valves to the drive-free state; and
control means for performing the following steps when the intake
valves and the exhaust valves of the partial cylinders are switched
from one of the driving state and the drive-free state to the other
of said states, said steps including: performing hydraulic pressure
switching by one of said control valve on the intake side and said
control valve on the exhaust side ahead of hydraulic pressure
switching by the other of said control valves; counting a
subsequent number of rotations of a crankshaft of the engine; and,
when the counted number of rotations has reached a predetermined
value, performing hydraulic pressure switching by the other of said
control valves, said predetermined value being set such that
driving of, or resumption of driving of, said intake valves and
said exhaust valves for all suspended cylinders is made in a given
order irrespective of a rotational frequency of the engine.
2. The apparatus for controlling a multi-cylinder internal
combustion engine according to claim 1, wherein, at the time of
switching from the all-cylinder operation to the partial-cylinder
operation, a throttle opening degree of the engine is switched to
that throttle opening degree for the partial-cylinder operation
which is set such that an engine output torque does not change
before and after the switching, further comprising throttle control
means which changes the throttle opening degree by a predetermined
amount toward the throttle opening degree for the partial-cylinder
operation when an engine operating state has fallen into a
predetermined operating region for performing the partial-cylinder
operation and thereafter switches to the partial-cylinder
operation.
3. The apparatus for controlling a multi-cylinder internal
combustion engine according to claim 1, wherein, at the time of
switching from the all-cylinder operation to the partial-cylinder
operation, a throttle opening degree of the engine is switched to
that throttle opening degree for the partial-cylinder operation
which is set such that an engine output torque does not change
before and after the switching, further comprising throttle control
means which makes the throttle opening degree, for an initial
predetermined period of time after having switched to the
partial-cylinder operation, to a throttle opening degree which
exceeds said throttle opening degree for the partial-cylinder
operation.
4. The apparatus for controlling a multi-cylinder internal
combustion engine according to claim 1, wherein, at the time of
switching from the all-cylinder operation to the partial-cylinder
operation, a throttle opening degree of the engine is switched to
that throttle opening degree for the partial-cylinder operation
which is set such that an engine output torque does not change
before and after the switching, further comprising: first throttle
control means which changes the throttle opening degree by a
predetermined amount toward the throttle opening degree for the
partial-cylinder operation when an engine operating state has
fallen into a predetermined operating region for performing the
partial-cylinder operation and thereafter switches to the
partial-cylinder operation; and second throttle control means which
makes the throttle opening degree, for an initial predetermined
period of time after having switched to the partial-cylinder
operation, to a throttle opening degree which exceeds said throttle
opening for the partial-cylinder operation.
5. The apparatus for controlling a multi-cylinder internal
combustion engine according to claim 1, further comprising
correcting means which sets a correcting coefficient for the
all-cylinder operation and a correcting coefficient for the
partial-cylinder operation which is larger than the correcting
coefficient for the all-cylinder operation, said correcting
coefficients serving as temperature correcting coefficients for
increasing, at a time of low temperature, the throttle opening
degree depending on an engine temperature, said correcting means
operating to switch the temperature correcting coefficients between
the correcting coefficient for the all-cylinder operation and the
correcting coefficient for the partial-cylinder operation depending
on whether the operation is in the all-cylinder operation or in the
partial-cylinder operation.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for controlling a
multi-cylinder internal combustion engine with partial cylinder
switch-off mechanism. The engine is capable of regulating the
number of cylinders in operation between the following two modes,
one being a mode in which all cylinders are operated (hereinafter
called "all-cylinder operation"), the other being a mode in which
some cylinders are operated while the other cylinders (i.e.,
partial cylinders) are suspended in operation by switching them off
(hereinafter called "partial-cylinder operation").
2. Description of the Related Art
This type of conventional multi-cylinder internal combustion engine
is provided with hydraulically operated valve switching means on an
intake side and on an exhaust side, respectively, to switch intake
valves and exhaust valves for part of cylinders between a driving
state and a state in which the driving of the valves is stopped or
suspended (also called a "drive-free state"). At the time of
partial-cylinder operation, the intake valves and the exhaust
valves of part of the cylinders are switched to the drive-free
state.
In order to avoid a loss in torque due to compression of intake air
at a compression stroke or at an exhaust stroke in cylinders not in
operation (hereinafter also called "suspended cylinders"), the
driving of inlet valves must be stopped ahead of, or prior to,
exhaust valves at the time of switching from the all-cylinder
operation to the partial-cylinder operation. On the other hand, in
order to prevent oil from flowing into the suspended cylinders, the
driving of the exhaust valves must be stopped ahead of the intake
valves at the time of switching from the all-cylinder operation to
the partial-cylinder operation. Further, in order to avoid a
deviation in an air/fuel ratio at the time of returning back to the
all-cylinder operation, due to gas which may remain in the
suspended cylinders, the exhaust valves must be returned to driving
ahead of the intake valves at the time of switching from the
partial-cylinder operation to the all-cylinder operation.
There is known an apparatus as described hereinbelow (see the item
entitled "Problems that the Invention is to Solve" in Japanese
Published Unexamined Patent Application No. 74545/1996). Namely, in
this conventional apparatus, in order to stop the driving of, or to
resume the driving of, one of the intake valves and the exhaust
valves ahead of the other thereof at the time of switching between
the all-cylinder operation and the partial-cylinder operation,
there is separately provided a control valve for switching the
input hydraulic pressure to each of valve switching means on the
intake side and on the exhaust side, respectively. At the time of
switching of operation, the control of switching of the hydraulic
pressure by the control valve on the intake side and the control of
switching of the hydraulic pressure by the control valve on the
exhaust side are performed at a predetermined time lag.
If the control valve on the intake side and the control valve on
the exhaust side are controlled at a time lag as in the
above-described conventional example, and at the time, e.g., of
switching from the all-cylinder operation to the partial-cylinder
operation, if the switching control of the hydraulic pressure by
the control valve on the exhaust side is performed at a
predetermined time after the switching control of the hydraulic
pressure by the control valve on the intake side has been finished,
there is the following possibility. Namely, in case the operation
of a plurality of cylinders is suspended, there is a possibility,
depending on a rotational frequency of the engine, that the
switching control of the hydraulic pressure is performed by the
control valve on the intake side during the compression stroke of
any one of the cylinders and that the switching control of the
hydraulic pressure by the exhaust valves is performed during the
ignition stroke. According to this arrangement, the exhaust valves
will no longer be opened in the exhaust stroke and, consequently,
the driving of the exhaust valves will substantially be stopped
ahead of the intake valves. Therefore, in the example of the
above-described conventional apparatus, there is no guarantee that
the driving of the intake valves and the exhaust valves in all of
the suspended cylinders is stopped or resumed in a given order.
In view of the above-described points, the present invention has an
object of providing an apparatus for controlling a multi-cylinder
internal combustion engine, in which it is possible to stop the
driving of, or to resume the driving of, the intake valves and the
exhaust valves for all of the suspended cylinders in a given order
irrespective of the rotational frequency of the engine.
SUMMARY OF THE INVENTION
In order to attain the above and other objects, the present
invention is an apparatus for controlling a multi-cylinder internal
combustion engine with partial cylinder switch-off mechanism. The
engine is switchable between an all-cylinder operation in which all
cylinders are operated and a partial-cylinder operation in which
operation of partial cylinders is suspended. The apparatus
comprises: hydraulically operated valve switching means on an
intake side and on an exhaust side, respectively, for switching
intake valves and exhaust valves of the partial cylinders between a
driving state and a drive-free state, wherein the intake valves and
the exhaust valves of the partial cylinders are switched, during
the partial-cylinder operation, into the drive-free state; a
control valve on the intake side for switching a hydraulic pressure
inputted to the hydraulically operated valve switching means on the
intake side between a hydraulic pressure to bring the intake valves
into the driving state and a hydraulic pressure to bring the intake
valves to the drive-free state; a control valve on the exhaust side
for switching a hydraulic pressure inputted to the hydraulically
operated valve switching means on the exhaust side between a
hydraulic pressure to bring the exhaust valves into the driving
state and a hydraulic pressure to bring the exhaust valves to the
drive-free state; and control means for performing the following
steps when the intake valves and the exhaust valves of the partial
cylinders are
switched from one of the driving state and the drive-free state to
the other of the states. The steps include: performing hydraulic
pressure switching by one of the control valve on the intake side
and the control valve on the exhaust side ahead of hydraulic
pressure switching by the other of the control valves; counting a
subsequent number of rotation of a crank shaft of the engine; and,
when the counted number of rotation has reached a predetermined
value, performing hydraulic pressure switching by the other of the
control valves.
Talking about an example when the intake valves and the exhaust
valves of the partial cylinders are switched from the driving state
to the drive-free state, an explanation is made about the case in
which the driving of the intake valves is stopped ahead of (or
prior to) the exhaust valves so that the exhausting from the
suspended cylinders is stopped after the air intake into the
suspended cylinders has been stopped. In such a case, the
above-described predetermined value is set depending on that number
of rotation of the crank shaft which is required by the crank shaft
from the point of time of performing the control of switching the
hydraulic pressure by the control valves on the intake side to the
point of time of completion of the intake stroke of all the
suspended cylinders. By employing this arrangement, the driving of
the exhaust valves is stopped after the air intake into all of the
suspended cylinders has been stopped.
As described above, according to the present invention, the
stopping of the driving of, or the resumption of the driving of,
the intake valves and the exhaust valves can be performed in a
given order with respect to all of the suspended cylinders,
irrespective of the rotational frequency of the engine.
In the embodiment to be described hereinafter, what corresponds to
the above-described control means is the processing from step S9-5
to step S9-9 in FIG. 5 and the processing from step S26-1 to step
S26-7 in FIG. 6. A set value NVTEXDO at step S9-2 in FIG. 5 and a
set value NCSENDO at step S26-3 in FIG. 6 correspond to the
above-described predetermined value.
In the multi-cylinder internal combustion engine with partial
cylinder switch-off mechanism, the output torque is likely to
fluctuate at the time of switching from the all-cylinder operation
to the partial-cylinder operation, thereby giving rise to
shocks.
In order to eliminate this kind of disadvantage in the occurrence
of shocks, there has hitherto been known the following. Namely, as
disclosed in Japanese Published Unexamined Patent Application No.
103430/1987, there is provided a controller which electronically
controls a throttle opening degree of an engine via an electric
motor or the like. When the engine operation is switched from the
all-cylinder operation to the partial-cylinder operation, the
throttle opening degree of the engine is switched to that throttle
opening degree for the partial-cylinder operation which is set such
that an engine output torque does not change before and after the
switching, whereby the fluctuation in torque at the time of
switching is prevented. However, even if the throttle opening
degree is changed, at the time of switching to the partial-cylinder
operation, to the throttle opening degree for the partial-cylinder
operation, the amount of air intake into the suspended cylinders
does not change immediately. Due to this delay in response, the
engine output torque temporarily fluctuates, resulting in the
occurrence of the torque shocks.
As a solution to the problem, it is preferable to provide: first
throttle control means which changes the throttle opening degree by
a predetermined amount toward the throttle opening degree for the
partial-cylinder operation when an engine operating state has
fallen into a predetermined operating region for performing the
partial-cylinder operation and thereafter switches to the
partial-cylinder operation; and second throttle control means which
makes the throttle opening degree, for an initial predetermined
period of time after having switched to the partial-cylinder
operation, to a throttle opening degree which exceeds the throttle
opening for the partial-cylinder operation. The above-described
predetermined period of time is arbitrarily set within a range
which can improve the delay in response in the amount of intake air
at an initial period after switching to the partial-cylinder
operation.
As a result of the change by the first throttle control means of
the throttle opening degree before switching to the
partial-cylinder operation, the delay in response in the amount of
intake air after the switching from the all-cylinder operation to
the partial-cylinder operation is improved. Further, as a result of
an overshooting control by the second throttle control means of the
throttle opening degree at an initial period after switching to the
partial-cylinder operation, the amount of intake air varies
quickly. In this manner, the amount of intake air changes with good
response to the value which corresponds to the throttle opening
degree for the partial-cylinder operation. The temporary
fluctuations in the engine output torque at the time of switching
to the partial-cylinder operation can thus be restricted, thereby
reducing the torque shocks to the best extent possible.
The change in the throttle opening degree with the first throttle
control means is performed during the all-cylinder operation. It
follows that, if the above-described predetermined amount is set to
a large amount, the engine output torque excessively changes
immediately before switching to the partial-cylinder operation,
with the result that the torque shocks occur at the time of
switching from the all-cylinder operation to the partial-cylinder
operation. Therefore, the above-described predetermined amount
should be set to such a value that the amount of intake air begins
to change at the time of switching.
By performing even one of the change in the throttle opening degree
before switching to the partial-cylinder operation and the
overshooting control in the throttle opening degree at an initial
period after the switching, the delay in response in the amount of
intake air can be improved to thereby reduce the torque shocks to a
certain degree. Therefore, only one of the above-described first
throttle control means and the second throttle control means may be
provided.
In the embodiment to be described hereinafter, what corresponds to
the above-described first throttle control means is the processing
from step S4 to step SB in FIG. 3. What corresponds to the
above-described second throttle control means is the processing
from step S11 to step S17 in FIG. 3.
Before the engine has been warmed up, the friction loss in the
engine is large. As a result, the lower the temperature becomes,
the larger becomes the throttle opening degree which is required to
obtain the same output torque. As a solution, there is
conventionally known the following. Namely, a setting is made of a
temperature correction coefficient depending on the engine
temperature, e.g., a cooling water temperature. The throttle
opening degree at the time of low water temperature is thus
corrected to increase it.
However, in the multi-cylinder internal combustion engine with
partial cylinder switch-off mechanism, the friction loss in the
suspended cylinders at the time of partial-cylinder operation must
be covered or supplemented by the remaining cylinders. If the
partial-cylinder operation is performed at the time of low water
temperature, the friction loss in the suspended cylinders can no
longer be covered by the remaining cylinders in operation, with the
result that the operating state of the engine becomes unstable. As
a solution, it is conventionally so arranged that the all-cylinder
operation is performed, even in the partial-cylinder operation
region, at the time of low water temperature (see operation manual
'92-10, No. 103681 of a new model car called by a pet name of
"Mirage.Lancer" manufactured by Mitsubishi Jidosha Kogyo Kabushiki
Kaisha). In the arrangement of this prior art, however, the
partial-cylinder operation is prohibited at the time of low water
temperature. This will be a disadvantage in an attempt to improve
the specific fuel consumption by adopting the partial-cylinder
operation.
It is preferable to provide correcting means which sets a
correcting coefficient for the all-cylinder operation and a
correcting coefficient for the partial-cylinder operation which is
larger than the correcting coefficient for the all-cylinder
operation, the correcting coefficients serving as temperature
correcting coefficients for increasing, at a time of low
temperature, the throttle opening degree depending on an engine
temperature, the correcting means operating to switch the
temperature correcting coefficients between the correcting
coefficient for the all-cylinder operation and the correcting
coefficient for the partial-cylinder operation depending on whether
the operation is in the all-cylinder operation or in the
partial-cylinder operation. According to this arrangement, the
correction amount for increasing the throttle opening degree at the
time of low temperature becomes larger in the partial-cylinder
operation than in the all-cylinder operation. The friction loss in
the suspended cylinders is thus compensated for by an increase in
the output due to an increase in the amount of intake air into the
cylinders in operation. Therefore, even if the partial-cylinder
operation is performed at the time of low temperature, the engine
can be operated stably. As a result, it becomes possible to perform
the partial-cylinder operation at the time of low temperature.
In the embodiment to be described hereinafter, what corresponds to
the above-described correction means is the processing for
computing a command value for the throttle opening degree THCMD as
shown in FIG. 4. In the embodiment to be described hereinafter, the
cooling water temperature was used as a parameter to show the
engine temperature. However, other than the cooling water
temperature, such as the oil temperature of the engine lubricating
oil, may also be used as long as it relates to the engine
temperature. The above-described low temperature means the state
before the engine has completed its warming up and means below
80.degree. C., for example, in case of the cooling water
temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and the attendant advantages of the
present invention will become readily apparent by reference to the
following detailed description when considered in conjunction with
the accompanying drawings wherein:
FIG. 1 is a schematic diagram showing an example of an engine to
which the apparatus of the present invention is applied;
FIG. 2 is a schematic diagram showing switching means which
switches intake valves and exhaust valves between a driving state
and a drive-free state;
FIG. 3 is a flow chart showing a switching control program for
switching between an all-cylinder operation and a partial-cylinder
operation;
FIG. 4A is a flow chart showing a program for computing a command
value of a throttle opening degree, and FIG. 4B is a graph showing
table data of correction coefficients for the all-cylinder
operation and the partial-cylinder operation, for correcting the
throttle opening degree depending on a water temperature;
FIG. 5 is a flow chart showing a program for switching to the
partial-cylinder operation;
FIG. 6 is a flow chart showing a program for switching back to the
all-cylinder operation;
FIG. 7 is a time chart showing the changes in the throttle opening
degree or the like by the control shown in FIG. 3; and
FIG. 8 is a graph showing the changes in the throttle opening
degree, the amount of air intake, and an output torque.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
FIG. 1 shows a six-cylinder V-type engine in which three cylinders
2 are disposed in a pair of first and second banks 1.sub.1,
1.sub.2, respectively. There are provided an intake manifold 3
which is common to both the banks 1.sub.1, 1.sub.2, and separate
exhaust manifolds 4.sub.1, 4.sub.2 for the first bank 1.sub.1 and
for the second bank 1.sub.2, respectively. A throttle valve 5 is
interposed on an upstream side of the intake manifold 3. A fuel
injection valve 6 is provided in each of the branches which lie on
a downstream side of the intake manifold 3 and which are in
communication with respective cylinders 2. It is thus so arranged
that each of the cylinders 2 can be supplied with fuel from each of
the fuel injection valves 6.
The throttle valve 5 is driven to be opened and closed by an
electric motor 5a. A throttle opening degree TH is electronically
controlled by a controller 7 which is made up of a microcomputer
for controlling the electric motor 5a.
It is also so arranged that the driving to open and close intake
valves and exhaust valves for the cylinders 2 in the first bank
1.sub.1 can be stopped, whereby the cylinders 2 in the first bank
1.sub.1 are suspended in operation (or are allowed to be
drive-free). As shown in FIG. 2, a valve driving cam mechanism for
the cylinders 2 in the first bank 1.sub.1 has the following
construction. Namely, a pair of intake valves and a pair of exhaust
valves for each of the cylinders are driven to be opened and closed
via each pair of free rocker arms 10.sub.1, 10.sub.2 on the intake
side and on the exhaust side, respectively, by means of those
driving rocker arms 9.sub.1, 9.sub.2 on the intake side and on the
exhaust side which come into contact with driving cams 8.sub.1,
8.sub.2 on the intake side and on the exhaust side, respectively,
on a cam shaft 8. There are provided hydraulically operated
changeover means 11.sub.1, 11.sub.2 on the intake side and on the
exhaust side which establish the connection, and release the
connection, between each of the driving rocker arms 9.sub.1,
9.sub.2 on the intake side and on the exhaust side and each pair of
the free rocker arms 10.sub.1, 10.sub.2. When the connection
between the driving rocker arms 9.sub.1, 9.sub.2 and the free
rocker arms 10.sub.1, 10.sub.2 is released, the free rocker arms
10.sub.1, 10.sub.2 remain in contact with circular idling cams
8.sub.3, whereby the intake valves and the exhaust valves are kept
closed. As a result, the operation mode is switched from an
all-cylinder operation mode in which all of the cylinders 2 in both
the banks 1.sub.1, 1.sub.2 are operated to a partial-cylinder
operation mode in which the operation of the cylinders 2 in the
first bank 1.sub.1 is suspended (or stopped).
Each of the changeover means 11.sub.1, 11.sub.2 on the intake side
and on the exhaust side is made up of: connecting pins 110 which
can be fitted through the respective driving rocker arms 9.sub.1,
9.sub.2 and the respective free rocker arms 10.sub.1, 10.sub.2 ;
pressure chambers 111 which are respectively formed in the driving
rocker arms 9.sub.1, 9.sub.2 so as to urge the connecting pins 110
toward the free rocker arms 10.sub.1, 10.sub.2 ; and a control
valve 112 which controls the hydraulic pressure in the pressure
chambers 111 via an oil passage 12a which is formed in each of
rocker arm shafts 12.sub.1, 12.sub.2 on the intake side and on the
exhaust side, respectively.
Each of the control valves 112 is provided with a spool 112d and a
solenoid valve 112g. The spool 112d is switchable between an open
position in which an output port 112a which is in communication
with the oil passage 12a is connected to an input port 112b which
is in communication with an oil supply passage 113, and a closed
position (i.e., the illustrated position) in which the
above-described connection is shut off to thereby connect the
output port 112a to a drain port 112c. The solenoid valve 112g is
controlled by the above-described controller 7 and is interposed in
a pilot passage 112f which inputs a hydraulic pressure from the oil
supply passage 113 into a pilot chamber 112e which urges the spool
112d towards the open position. When the solenoid valve 112g is
opened, the spool 112d is switched to the open position against a
spring 112h by the input of a hydraulic pressure into the pilot
chambers 112e. The pressure chambers 111 thus receive an input of
the hydraulic pressure and, as a result, the connecting pins 110
are urged into the free rocker arms 10.sub.1, 10.sub.2, whereby the
connection between the driving rocker arms 9.sub.1, 9.sub.2 and the
free rocker arms 10.sub.1, 10.sub.2 is released. Further, there is
provided a bypass orifice 112i which normally (i.e., always)
communicates the output port 112a with the input port 112b of the
control valve 112. It is thus so arranged that, when the spool 112d
is in the
closed position, the oil passage 12a is filled with low-pressure
oil. In this arrangement, by switching the spool 112d to the open
position, the hydraulic pressure in the oil passage 12a, i.e., in
the pressure chambers 111, can be boosted with a good response.
Even if the hydraulic pressure in the pressure chambers 111 is
boosted, the connecting pins 110 are prevented, while the intake
valve and the exhaust valve are in the period of being opened, from
being pushed towards the free rocker arms 10.sub.1, 10.sub.2
because of the friction due to a shear force which works between
the driving rocker arms 9.sub.1, 9.sub.2 and the free rocker arms
10.sub.1, 10.sub.2. When the intake valves and the exhaust valves
have been closed, the connecting pins 110 will be forced into the
free rocker arms 10.sub.1, 10.sub.2, whereby the connection between
the driving rocker arms 9.sub.1, 9.sub.2 and the free rocker arms
10.sub.1, 10.sub.2 is released. In the figure, reference numeral
114 is a normally closed hydraulic pressure switch which is
switched off when the hydraulic pressure in the output port 112a of
the control valve 112 has risen. Reference numeral 12b is an oil
passage for lubricating oil which is formed in the rocker arm
shafts 12.sub.1, 12.sub.2.
The above-described controller 7 receives inputs in the form of
signals from the following sensors, namely: a sensor 13.sub.1 for
detecting an amount of depressing an accelerator pedal AP
(hereinafter called an accelerator opening degree); a sensor
13.sub.2 for detecting a throttle opening degree TH; a sensor
13.sub.3 for detecting a rotational frequency of the engine NE; a
sensor 13.sub.4 for detecting a temperature of cooling water TW; a
sensor 13.sub.5 for detecting a vehicle speed V; a pulse generator
13.sub.6 for generating a pulse of a predetermined phase
(hereinafter celled a TDC signal) at every one revolution of a
crank shaft of the engine; and respective hydraulic pressure
switches 114 for the changeover means 11.sub.1, 11.sub.2 on the
intake side and on the exhaust side. Based on these signals,
control is made of the throttle opening degree TH and of the
solenoid valve 112g for the switching means 11.sub.1, 11.sub.2 on
the intake side and on the exhaust side (In this specification, the
reference characters, etc. are normally given at the end of the
whole description. For example, the "rotational frequency `NE` of
the engine" is described as the "rotational frequency of the engine
`NE`").
The details of the control are shown in FIG. 3. This control is
performed once each time a TDC signal is inputted. First, at step
S1, the opening degree for the all-cylinder operation THN and the
opening degree for the partial-cylinder operation THS are obtained.
The value THN is that throttle opening degree at the time of
all-cylinder operation which is necessary to obtain a predetermined
output torque of the engine in each of the operating states which
are defined with the accelerator opening degree AP and the
rotational frequency of the engine NE as parameters. The value THS
is that throttle opening degree at the time of partial-cylinder
operation which is necessary to obtain the same output torque as at
the time of all-cylinder operation in each of the operating states.
Both THN and THS are stored as map data with AP and NE as
parameters. THN and THS which correspond to AP and NE at the
present time are searched.
Then, at step S2, a discrimination is made as to whether a flag
showing that the conditions for partial-cylinder operation have
been met, FST, is set to 1. The time when the operation of the
cylinders 2 in the first bank 1.sub.1 can be suspended or stopped
in operation is when a stable operation can be maintained by the
operation of the cylinders 2 in the second bank 1.sub.2 alone,
namely, when the following three specific conditions have been met:
i.e., when the rotational frequency of the engine NE is in a medium
speed range (e.g., 1500 rpm<NE<3500 rpm); when the vehicle
speed V is above a speed at which the start of the vehicle running
has been finished (e.g., V>15 km/h); and when the engine is
under a low load (e.g., 0.5.degree.<TH<) 20.degree.). FST is
set to 1 by a background processing when the above three conditions
have been met.
If FST=1, the program proceeds to step S3, where a discrimination
is made as to whether a flag showing that the cylinders are being
suspended in operation, FOUT, is set to 1. The flag FOUT is
initially reset to 0 and, at the time of switching from the
all-cylinder operation to the partial-cylinder operation, a
discrimination is made that FOUT.noteq.1, whereby the program
proceeds to step S4. At step S4, a discrimination is made as to
whether the flag showing that the cylinders are in the process of
switching to the partial-cylinder operation, FIN, is set to 1. The
flag FIN is also initially reset to 0 and therefore a
discrimination of FIN.noteq.1 is made. The program thus proceeds to
step S5, where an amount of change in the throttle opening degree
before the switching operation, THCS1, is obtained. THCS1 is stored
as map data with the accelerator opening degree AP and the engine
rotational frequency NE as parameters. THCS1 corresponding to the
AP and NE at the present moment are searched in the map. Then, the
program proceeds to step S6 where, in order to flatten (or smooth)
the throttle opening degree by the amount of THCS1, a flattened
value DTHCS1 is computed by dividing THCS1 by a predetermined
number of flattening operations NTHCS1. At the next step S7, FIN is
set to 1 and, at step S8, the amount of change in the throttle
opening degree THCS is made to be a value which is obtained by
adding DTHCS1 to a previous value.
Thereafter, the program proceeds to step S9, where a processing of
switching to the partial-cylinder operation is performed. This
operation is described in more detail hereinbelow. The program then
proceeds to step S10, where a command value THCMD of the throttle
opening degree is computed, thereby completing one round of control
operations. Details of computing THCMD are shown in FIG. 4A. First,
at step S10-1, a discrimination is made as to whether the flag for
selecting the opening degree for the partial-cylinder operation,
FTHS, is set to 1. Since the flag FTHS has initially been reset to
0, a discrimination is made that FTHS.noteq.1. The program thus
proceeds to step S10-2, where a basic command value of the throttle
opening degree THCMDB is made to be a value which is obtained by
adding the change amount THCS to the throttle opening degree for
the all-cylinder operation THN. Then, at step S10-3, an actual
command value of the throttle opening degree, THCMD, is made to be
a value which is obtained by multiplying THCMDB by a correction
factor for the all-cylinder operation, KTWN, depending on the water
temperature TW. When FTHS is set to 1, THCMD is made at step S10-4
to be the opening degree for the partial-cylinder operation THS.
Thereafter, at step S10-5, THCMDB is made to be a value which is
obtained by multiplying THCMDB by a correction factor for the
partial-cylinder operation, KTWS, depending on the water
temperature TW.
Before the engine has been warmed up, the friction loss in the
engine is large and, the lower the temperature is, the larger
becomes the throttle opening degree which is required to obtain the
same output torque. Particularly, at the time of the
partial-cylinder operation, the friction loss on the side of the
first bank 1.sub.1 must be covered or supplemented by the side of
the second bank 1.sub.2. Therefore, if the correction factor
depending on the water temperature TW is made the same with each
other at the time of the all-cylinder operation and at the time of
the partial-cylinder operation, the engine can no longer be stably
operated, in case the partial-cylinder operation is performed
before the engine has been warmed up. As a solution, in the
embodiment of the present invention, the correction factor
depending on the water temperature TW is exchanged between KTWN at
the time of the all-cylinder operation and KTWS at the time of the
partial-cylinder operation. The correction factor for the
partial-cylinder operation KTWS is set larger, as shown in FIG. 4B,
than the correction factor for the partial-cylinder operation KTWN.
It is thus so arranged that the engine can be stably operated even
if the partial-cylinder operation is performed before the engine
warming up has been completed. Consequently, it becomes possible to
perform the partial-cylinder operation even before the completion
of the engine warming up, resulting in an improvement in the
specific fuel consumption of the internal combustion engine.
Once the first round of control operations has been finished as
described above, in the next round, a discrimination of FIN=1 is
made at step S4 because FIN has been set to 1 at step S7 last time.
The program thus proceeds to step S11, where a discrimination is
made as to whether a counter value to hold the amount of change
after the switching operation, NTHHLD, has become 0. NTHHLD is
initially set to a predetermined set value NTHHLDO. Therefore, a
discrimination of NTHHLD.noteq.0 is made, and the program proceeds
to step S12, where a discrimination is made as to whether a flag
for cutting fuel FFC is set to 1. Since FFC is initially set to 0,
a discrimination of FFC.noteq.1 is made, and the program proceeds
to step S13. At step S13, a discrimination is made as to whether an
absolute value of a sum of the previous value of the amount of
change in the throttle valve opening degree, THCS, and the
flattened value DTHCS1 is below an absolute value of the amount of
change in the throttle valve opening degree before the switching
operation, THCS1. Until the condition of
.vertline.THCS+DTHCS1.vertline.>.vertline.THCS1.vertline. has
been met, the program proceeds to step S8, where THCS is changed
stepwise by DTHCS1 each time the TDC signal is inputted. Therefore,
as shown in range "A" in FIG. 7, the basic command value of the
throttle opening degree THCMDB gradually changes from the opening
degree for the all-cylinder operation THN.
Once THCS has become equal to THCS1, the program proceeds to step
S14, where NTHHLD is deducted by 1. Then, at step S15, FFC is set
to 1, and the fuel supply to the cylinders 2 in the first bank
1.sub.1 is stopped. Then, the program proceeds to step S16, where
an amount of change in the throttle opening degree after the
switching operation, THCS2, is obtained. THCS2 is stored as map
data with the accelerator opening degree AP and the engine
rotational frequency NE as parameters. THCS2 corresponding to AP
and NE at the present time is searched in the map. Then, the
program proceeds to step S17, where the amount of change in the
throttle opening degree THCS is made to THCS2, and the program
proceeds to step S9 and following steps to thereby complete the
control operations in this round.
Next time, since FFC has been set to 1 at step S15 last time, the
program proceeds to step S14 and following steps from step S12
without passing through step S13. Then, this processing is repeated
from the time when FFC was set to 1, i.e., from the time when the
operation was switched to the partial-cylinder operation as a
result of stopping of the fuel supply to the cylinders 2 in the
first bank 1.sub.1, to the time when the TDC signal has been
inputted in the same number of times as that of NTHHLDO. The basic
command value of the throttle opening degree THCMDB is maintained,
as shown in range B in FIG. 7, at a value which is obtained by
adding THCS2 to the opening degree for the all-cylinder operation
THN.
Once NTHHLD has become 0 as a result of inputting the TDS signal in
the same number of times as that of NTHHLDO, the program proceeds
from step S11 to step S18, where a discrimination is made as to
whether the flag for selecting the throttle opening degree for the
partial-cylinder operation FTHS is set to 1. FTHS is initially
reset to 0 and therefore a discrimination of FTHS.noteq.1 is made,
and the program proceeds to step S19, where THCS2 corresponding to
AP and NE at the present time is searched in the map. Then, the
program proceeds to step S20, where a counter value of performing
the flattening operations kF is added by 1. The program thereafter
proceeds to step S21, where THCS is made to the value which is
obtained by the following formula
NTHCS2 is the number of flattening to flatten or smooth the
throttle opening degree from a value which is obtained by adding
the amount of change after the switching operation, THCS2, to the
throttle opening degree for the all-cylinder operation, THN, to the
throttle opening degree for the partial-cylinder operation, THS. At
step S22, a discrimination is made as to whether kF has become the
same in number as NTHCS2 or more. While kF<NTHCS2, the
above-described processing is repeated. Each time the TDC signal is
inputted, THCS changes stepwise by the flattening amount DTHCS2
which is obtained by substituting THN, THL and THCS2 corresponding
to AP and NE at that point of time in the following formula
In this manner, as shown in range C in FIG. 7, the basic command
value for the throttle opening degree THCMDB gradually changes to
THS from the value at the beginning of switching which is obtained
by adding THCS2 to THN.
Once kF has become the same in number as NTHCS2, the program
proceeds to step S23, where THCS and kF are respectively reset to 0
and, at step S24, FTHS is set to 1 and the program proceeds to step
S9 and following steps. From the next time, a discrimination of
FTHS=1 is made at step S18, and the program proceeds directly from
step S18 to step S9 and following steps. In this manner, as shown
in range D in FIG. 7, the basic command value of the throttle
opening degree, THCMDB, is maintained at the throttle opening
degree for the partial-cylinder operation THS.
The above-described amount of change before the switching
operation, THCS1, is set to such a value that the intake air amount
begins to change at the point of time of switching the operation to
the partial-cylinder operation. The above-described amount of
change after the switching operation, THCS2, is set to a value
which is larger than the deviation between the throttle opening
degree for the all-cylinder operation, THN, and the throttle
opening degree for the partial-cylinder operation, THS. Further,
the above-described holding counter set value NTHHLDO is stored as
table data with the engine rotational frequency NE as a parameter
and is set with a co-relationship with THCS2 so as to become a
value which is necessary and sufficient for the intake air amount
to be changed to an amount which corresponds to THS. FIG. 8 shows
the changes in the throttle opening degree, the intake air amount,
and the output torque of the engine. In the figure, solid lines
show the change characteristics when the engine is controlled as
described above. As compared with those dotted lines in the figure
which show the change characteristics when the throttle opening
degree is changed from THN to THS at the point of time of switching
the throttle opening degree to the partial-cylinder operation, the
intake air amount changes with good response to the amount
corresponding to THS. As a result, temporary torque changes at the
time of switching operation can be restricted and the torque shocks
can be reduced to the best extent possible.
Depending on the operating conditions, the throttle opening degree
for the partial-cylinder operation THS sometimes becomes smaller
than that of the all-cylinder operation THN. In such a case, each
of the above-described change amounts THCS1, THCS2 is set to a
negative value. The above-described number of flattening NTHCS1 is
stored as table data with the engine rotational frequency NE as a
parameter, and the data setting is made such that the time required
to change the throttle opening degree by an amount corresponding to
THCS1 becomes constant irrespective of the engine rotational
frequency NE. Further, the above-described number of flattening
NTHCS2 is also stored as table data with the engine rotational
frequency NE as a parameter, and is set to a minimum value required
to prevent the torque changes at the time of change from THN+THCS2
to THS.
The processing of switching to partial-cylinder operation which is
performed at step S9 is shown in FIG. 5. First, at step S9-1, a
discrimination is made as to whether FFC is set to 1. A
discrimination of FFC.noteq.1 is made until FFC is set to 1 at step
S15. In this case, the program proceeds to step S9-2, where a
counter value for the suspension of the air intake valves NVTIND, a
counter value for the suspension of the exhaust valves, NVTEXD, and
a counter value for holding the change amount after the switching
operation, NTHHLD, are set to NVTINDO, NVTEXDO, NTHHLDO,
respectively. Once FFC has been set to 1, the program proceeds to
step S9-3, where a discrimination is made as to whether NVTIND has
become 0. As long as NVTIND.noteq.0, the program proceeds to step
S9-4 to deduct NVTIND by 1. Then, when FFC has been set to 1 and
the TDS signal has been inputted for the same number of times as
that of NVTINDO, whereby a condition of NVTIND=0 has been met, the
program proceeds to step S9-5. At this step S9-5, the solenoid
valve 112g for the switching means 11.sub.1 on the intake side is
opened to release the connection between the driving
rocker arms 9.sub.1 on the intake side and the free rocker arms
10.sub.1, 10.sub.1, whereby the driving of the intake valves of the
cylinders 2 in the first bank 1.sub.1 is stopped. NVTINDO is set to
secure cycles necessary to attain complete combustion and
exhausting of the fuel supplied before stopping the fuel supply. In
FIG. 7, NVTINDO is set to 6 so that the driving of the intake
valves is stopped after 6 numbers of rotations of the crank shaft
from the stopping of the fuel supply.
When the solenoid valve 112g for the switching means 11.sub.1 on
the intake side is opened, a discrimination is then made at step
S9-6 as to whether the hydraulic pressure switch 114 of the
switching means 11.sub.1 on the intake side has been switched off,
i.e., as to whether the hydraulic pressure in the switching means
11.sub.1 has actually increased. When the hydraulic pressure has
increased, the program proceeds to step S9-7, where a
discrimination is made as to whether NVTEXD has become 0. While
NVTEXD.noteq.0, the program proceeds to step S9-8, where NCTEXD is
deducted by 1. Then, when the hydraulic pressure in the switching
means 11.sub.1 on the intake side has risen and the TDS signal has
been inputted in the same number of times as that of the NVTEXDO,
whereby the condition of NVTEXD=0 has been met, the program
proceeds to step S9-9. At this step S99, the solenoid valve 112g
for the switching means 112 on the exhaust side is opened to
release the connection between the driving rocker arms 9.sub.2 on
the exhaust side and the free rocker arms 10.sub.2, 10.sub.2,
whereby driving of the exhaust valves of the cylinders 2 in the
first bank 1.sub.1 is stopped. Then, at step S9-10, a
discrimination is made as to whether the hydraulic pressure switch
114 of the switching means 11.sub.2 on the exhaust side has been
switched off, i.e., whether the hydraulic pressure in the switching
means 11.sub.2 has actually increased. When the hydraulic pressure
has risen, the program proceeds to step S9-11, where a
discrimination is made as to whether FTHS is set to 1. When FTHS
has been set to 1 at the above-described step S24, the program
proceeds to step S9-12, where FOUT is set to 1 and FIN is reset to
0.
NVTEXDO is set depending on that number of rotation of the crank
shaft which is required for the intake stroke of all of the
cylinders 2 in the first bank 1.sub.1 to complete after the
switching means 11.sub.1 on the intake side has been switched to
the side of stopping the valves. In FIG. 7, NVTEXDO is set to 2. In
this manner, irrespective of the rotational frequency of the
engine, the driving of the exhaust valves will be stopped after the
air intake into all of the cylinders 2 in the first bank 1.sub.1
has been stopped. Therefore, the torque loss in the compression
stroke and the exhaust stroke due to the compression of the intake
air can be prevented.
Once FOUT has been set to 1 at step S9-12, a discrimination of
FOUT=1 is made at step S3 in FIG. 3, and the program proceeds to
step S9 and following steps. As long as the operating states fall
within the operating range in which the conditions for the
partial-cylinder operation of FST=1 are met, the basic command
value of throttle opening degree, THCMDB, is maintained at the
throttle opening degree for the partial-cylinder operation,
THS.
When the operating state has fallen out of the range in which the
conditions for the partial-cylinder operation are met, whereby FST
is reset to 0, the program proceeds to step S25, where a
discrimination is made as to whether FOUT has been set to 1. If
FOUT=1, the program proceeds to step S26, where the processing for
returning all the cylinders back to operation is performed, and the
program then proceeds to step S10. The details of returning all the
cylinders back to operation are shown in FIG. 6. First, at step
S26-1, the solenoid valve 112g for the switching means 11.sub.2 on
the exhaust side is closed to thereby connect the driving rocker
arms 9.sub.2 on the exhaust side with the free rocker arms
10.sub.2, 10.sub.2, whereby the exhaust valves of the cylinders 2
of the first bank 1.sub.1 are returned back to the driving state.
Then, at step S26-2, a discrimination is made as to whether the
hydraulic pressure switch 114 of the switching means 11.sub.2 on
the exhaust side has been switched on, i.e., whether the hydraulic
pressure in the switching means 11.sub.2 has actually been lowered.
Until the hydraulic pressure has been lowered, the program proceeds
to step S26-3, where a counter value for returning the intake
valves, NCSEND, is set to a predetermined set value NCSENDO. Then,
the program proceeds to step S26-9 to make a discrimination as to
whether FTHS is set to 1. Since FTHS remains to be set to 1 at the
above-described step S24 at the time of partial-cylinder operation,
a discrimination of FTHS=1 is made. The first round of operations
is thus completed. Thereafter, when the hydraulic pressure has
risen, the program proceeds to step S26-4, where a discrimination
is made as to whether NCSEND has become 0. While NCSEND.noteq.0,
the program proceeds to step S26-5 to thereby deduct NCSEND by 1.
Thereafter, when the hydraulic pressure has risen and the TDC
signal has been inputted for the same number of times as that of
NCSENDO to thereby meet the condition of NCSEND=0, the program
proceeds to step S266. At this step, the solenoid valve 112g of the
switching means on the intake side 11.sub.1 is closed, and the
driving rocker arms 9.sub.1 on the intake side and the free rocker
arms 10.sub.1, 10.sub.1 are connected together, whereby the intake
valves of the cylinders 2 in the first bank 1.sub.1 are returned to
the driving state. Then, at step S26-7, a discrimination is made as
to whether the hydraulic pressure switch 114 for the switching
means 11.sub.1 on the intake side has been switched on. Namely, a
discrimination is made as to whether the hydraulic pressure in the
switching means 11.sub.1, on the intake side has actually been
lowered. When the hydraulic pressure in the switching means
11.sub.1 has actually been lowered, the program proceeds to step
S26-8, where FTHS and FCC are respectively reset to 0 to resume the
fuel supply to the cylinders 2 in the first bank 1.sub.1. The
all-cylinder operation is thus resumed.
Then, the program proceeds to step S26-9, where a discrimination of
FTHS.noteq.1 is made this time. The program then proceeds to step
S26-10, where a counter value for flattening operation kR is added
by 1, and then proceeds to step S26-11, where THCS is made to the
value to be obtained by the following formula
NTHCS3 is the number of flattening operations in order to change,
by flattening, the throttle opening degree from the opening degree
for the partial-cylinder operation, THS, to the opening degree for
the all-cylinder operation, THN. At step S26-12, a discrimination
is made as to whether kR has become equal in number to, or above,
NTHCS3. As long as kR<NTHCS3, the above-described processing is
repeated. Therefore, each time the TDC signal is inputted, THCS
changes stepwise by the amount of flattening DTHCS3 which is
obtained by substituting THN and THS corresponding to AP and NE
respectively at that point of time in the following formula
In this manner, the basic command value for the throttle opening
degree, THCMDB, gradually changes, as shown in range E in FIG. 7,
from THS to THN.
Once kR has become equal in number to NTHCS3, the program proceeds
to step S26-13, where THCS, kR, and FOUT are respectively reset to
0. As a result, the basic command value for the throttle opening
degree THCMDB is maintained at the opening degree for the
all-cylinder operation THN. Next time, a discrimination of
FOUT.noteq. is made at step S25 in FIG. 3, and the program proceeds
to step S27, where a discrimination is made as to whether FIN is
set to 1. FIN has been reset to 0 at step S9-12 at the time of the
partial-cylinder operation. Therefore, a discrimination of
FIN.noteq.1 is made and the program proceeds to step S28, where kF
is reset to 0. The program then proceeds to step S9 and following
steps. If the operating states fall out of the operating region
which meets the partial-operating conditions before setting FOUT
and resetting FIN at step S9-12, a discrimination of FOUT.noteq.1
is made at step S25 and also a discrimination of FIN=1 is made at
step S27. The program thus proceeds to step S11 and following
steps. Therefore, the control performed at the time of the
partial-cylinder operation is performed in succession. When the
setting of FOUT and the resetting of FIN have been performed at
step S9-12, the program proceeds to step S26 and the control to
return to the all-cylinder operation is performed.
The above-described NCSENDO is set depending on that number of
rotation of the crank shaft which is required for the exhaust
stroke to be completed in all of the cylinders 2 in the first bank
1.sub.1 after the switching means 11.sub.2 on the exhaust side is
switched to the valve driving side. In FIG. 7 NCSENDO is set to 2.
In this manner, at the time of returning to the all-cylinder
operation, the intake valves will be operated, irrespective of the
rotational frequency of the engine, after the exhausting of all the
cylinders in the first bank 1.sub.1 has been completed. As a
consequence, it is possible to perform the air intake after having
completely scavenged the residual gas containing oil that may have
flown into the cylinders 2 in the first bank 1.sub.1 as a result of
flowing in of oil during the partial-cylinder operation. This
brings about an improved accuracy of control in the air/fuel ratio.
The above-described number of flattening NTHCS3 is stored as table
data with the engine rotational frequency NE as a parameter and is
set to a minimum value that is required to prevent the torque
fluctuations at the time of change in the throttle opening degree
from THS to THN.
An explanation has so far been made about a six-cylinder V-type
engine. The present invention is, however, applicable to an example
in which the operation of part of the cylinders is suspended in a
multi-cylinder internal combustion engine in which the cylinders
are arranged in a line.
It is readily apparent that the above-described apparatus for
controlling a multi-cylinder internal combustion engine with
partial cylinder switch-off mechanism meets all of the objects
mentioned above and also has the advantage of wide commercial
utility. It should be understood that the specific form of the
invention hereinabove described is intended to be representative
only, as certain modifications within the scope of these teachings
will be apparent to those skilled in the art.
Accordingly, reference should be made to the following claims in
determining the full scope of the invention.
* * * * *